This invention relates to a method for assembling a tire on a wheel without causing excessive deformations of bead portions of the tire, and an apparatus for carrying out the method.
A method for assembling a tire on a wheel was disclosed in Japanese Utility Model Application Laid-open No. 50-104,302. In mounting a tire on a wheel with this prior art apparatus, the wheel is arranged on the flat support surface of a vertically movable table and fixed thereat by means of a center cone extensible and contractible relative to the table and fitted in a hub hole formed in the wheel at its center. The tire is then arranged on the wheel in an oblique state so that the part of one bead portion of the tire on the side of the table is loosely arranged around the well formed in the disc of the wheel.
On the other hand, guide rollers previously arranged on revolving arms so as to be coaxial to the axis of the center cone, respectively, while restraining rollers, are provided on the revolving arms so as to be vertically movable. By revolving the arms, the one bead portion of the tire is radially expanded by the guide rollers, and the side surface rubber is urged downward by the vertically movable restraining rollers. In this manner, the bead portions of the tire are fitted one by one or simultaneously on the rims of the wheel.
In the method of the prior art, however, the last part of the bead portion not yet arranged on the rim is deformed straight like a chord relative to the annular flange of the rim shortly before termination of the arranging operation of the bead portion. In this state, when the guide rollers and the restraining rollers are further rolled for arranging that part of the bead portion around the rim, that part is subjected to excessive external forces and locally bent or curved at the chord-shaped portion and, in a worst case, damaged. Even if the bead portion of the tire is not damaged, the deformed bead portion detrimentally affects the close contact between the wheel and the bead portions to lower the tire uniformity and sealing performance so that the inherent performance of the tire mounted on the wheel could not be exhibited.
In order to solve such a problem, Japanese Utility Model Application Publication No. 61-34,885 proposed an apparatus including restraining rollers elastically supported by springs and adapted to revolve along a plane in parallel with the bead portion of a tire arranged obliquely to a support surface. This maintains constant urging forces acting upon the tire. However, this method does not take into consideration compensation for the difference between diameters of a wheel flange and tire bead portions Even if the restraining rollers are caused to revolve obliquely along the inclined surface, the problem described above due to the external force locally acting upon the bead portions could not be advantageously solved.